There will be cancellations and delays to Air New Zealand long- haul flights for weeks as Rolls-Royce does urgent maintenance to is Boeing 787 engines. Earlier this week a flight to Japan had to turn back 20 minutes after take-off and shut down an engine as a precaution. In a second incident on Wednesday, a flight to Argentina was also forced to turn back. The Transport Accident Investigation Commission is investigating the two incidents. Mary Schiavo is an aviation lawyer and a former inspector general of the US Department of Transportation. She tells Guyon Espiner the main problem is with the turbine blades, which could spit out of the engine and hit a fuel line or a passenger.